I. Field of the Invention
The present invention relates to fluid systems, and more particularly, to a fluid device for indicating the rate of fluid flow through such systems, and new and improved means for biasing the indicator means towards a zero-flow position.
II. Description of the Prior Art
Positive displacement flow meters, such as described in my previous U.S. Pat. No. 3,282,102, issued on Nov. 1, 1966, have means for imparting a rotation to a shaft dependent upon the fluid flow rate through the flow meter. A pointer arm is secured to one end of the shaft externally of the flow meter and the pointer arm provides a visual indication of the rotation of the shaft and, hence, the rate of flow through the flow meter.
The fluid flow responsive means, such as the vane in my aforementioned patent, is operatively connected with the shaft which is biased toward a zero-flow position. To achieve this end, previously known flow meters have utilized a torsion spring to bias the shaft, and hence the fluid flow measuring means connected therewith, towards a zero-flow position. The previously known torsion spring biasing means, however, suffers several disadvantages of which it is the object of the present application to overcome.
One drawback of the previously known torsion springs for flow meters, is that the torsion spring is usually secured directly to the flow indicator housing. Since for durability the flow meter housings are constructed of metal, the metal to metal contact between the spring and the flow meter housing results in corrosion of the spring and subsequent spring failure.
Another disadvantage with the previously known flow meter torsion springs, is that pre-assembly of the torsion spring assembly is not feasible. Consequently when it becomes necessary to replace the torsion spring in an already installed flow meter, it is necessary to wind the torsion spring at the field location. Such a procedure is not only time consuming, but, in addition, due to unavoidable errors in manual installations, the tension on the torsion spring varies from one flow meter to another. Needless to say, differing spring tensions between otherwise identical flow meters result in inaccurate flow rate indications.